Thermal transfer sheet

Abstract

To provide a thermal-transfer sheet having a back layer that can be prepared without heat treatment such as aging and is superior in heat resistance and sliding property, and has no such defect of printed images as wrinkling and tailing during printing. A thermal-transfer sheet having a substrate film, a transfer ink layer formed on one face thereof, and a back layer formed on the other face thereof, the back layer comprising: a binder containing a polyamide-imide resin (A) having a Tg of 200° C. or higher and a polyamide-imide silicone resin (B) having a Tg of 200° C. or higher, as determined by differential thermal analysis, a mixture of a polyvalent metal salt (C) of alkylphosphoric ester and a metal salt (D) of alkylcarboxylic acid, a silicone oil (E), and an inorganic filler (F) containing fine particles (F 1 ) of an inorganic material having a Mohs' hardness of 3 or less alone or a mixture of fine particles (F 1 ) of an inorganic material and fine particles (F 2 ) of an inorganic material having a Mohs' hardness of more than 3, the metal salts (C) and (D) having an average particle size of 5 μm to 20 μm and the inorganic filler (F) having an average particle size of 0.05 to 5.5 μm.

1. A thermal-transfer sheet having a substrate film, a transfer ink layer formed on one face thereof, and a back layer formed on the other face thereof,
 the back layer comprising: 
 a binder containing a polyamide-imide resin (A) having a Tg of 200° C. or higher and a polyamide-imide silicone resin (B) having a Tg of 200° C. or higher, as determined by differential thermal analysis, 
 a mixture of a polyvalent metal salt (C) of alkylphosphoric ester and a metal salt (D) of alkylcarboxylic acid, 
 a silicone oil (E) in an amount of 1 to 30 parts with respect to 100 parts by mass of the binder, and 
 an inorganic filler (F) containing fine particles (F 1 ) of an inorganic material having a Mohs' hardness of 3 or less alone or a mixture of fine particles (F 1 ) of an inorganic material and fine particles (F 2 ) of an inorganic material having a Mohs' hardness of more than 3, 
 the metal salts (C) and (D) having an average particle size of 5 μm to 20 μm and the inorganic filler (F) having an average particle size of 0.05 to 5.5 μm. 
 
     
     
       2. The thermal-transfer sheet according to  claim 1 , wherein the blending ratio of the polyamide-imide resin (A) and the polyamide-imide silicone resin (B) is A:B=1:5 to 5:1 by mass. 
     
     
       3. The thermal-transfer sheet according to  claim 1  or  2 , wherein the blending ratio of the polyvalent metal salt (C) of alkylphosphoric ester and the metal salt (D) of alkylcarboxylic acid is C:D=1:9 to 9:1 by mass. 
     
     
       4. The thermal-transfer sheet according to  claim 1 , wherein the fine particles (F 1 ) are talc, mica, calcium carbonate, or a mixture thereof. 
     
     
       5. The thermal-transfer sheet according to  claim 1 , wherein the fine particles (F 2 ) are talc, mica, calcium carbonate or a mixture thereof. 
     
     
       6. The thermal-transfer sheet according to  claim 1 , wherein a content of the inorganic filler is 2 to 20 parts by mass with respect to 100 parts by mass of the binder. 
     
     
       7. The thermal-transfer sheet according to  claim 1 , wherein a thickness of the back layer is 0.30 to 0.60 g/m 2 .